The very presence of law—without which we cannot live as civilized people—is in conflict with the presence of virtue. Virtue—goodness—can only be chosen freely. If it is not chosen, it is not truly good. If I point a gun at you and order you to give money to charity, that does not make you charitable. It just means you’re afraid to die. To do good, and therefore to be good, you must be free of constraint and yet freely allow yourself to be ruled by God—like the Israelites before they had a king.
